JP6714529B2 - Electrostatic charging member for electrophotographic device and method for manufacturing charging member for electrophotographic device - Google Patents

Description

The present invention relates to a charging member for an electrophotographic apparatus, which is preferably used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile, which employs an electrophotographic method, and a method for manufacturing the charging member for an electrophotographic apparatus.

As a charging member of an electrophotographic apparatus, one having a base layer having rubber elasticity on the outer periphery of a core metal and a surface layer on the outer periphery of the base layer is known. Further, in the charging member, particles for forming roughness may be added to the binder resin in the surface layer due to, for example, charging characteristics. Then, Patent Document 1 discloses that porous resin particles and silicone oil are mixed with a binder resin in the surface layer. Further, Patent Document 2 discloses that in a coating layer, silicone oil having a reactive functional group is added to a fluororesin having active hydrogen.

JP, 2005-90454, A JP-A-2002-214879

In Patent Document 1, by mixing the porous resin particles and the silicone oil with the binder resin, Benard cells are prevented from occurring on the outer peripheral surface of the surface layer. This is to prevent the porous resin particles from being unevenly distributed in the boundary portion of the cells in the process of generation of Benard cells. Further, in Patent Document 2, bleeding of the silicone oil is suppressed by fixing the silicone oil to the fluororesin of the coating film layer through a reaction.

However, as a result of intensive studies by the present inventors, it was found that it is more advantageous in terms of improving image quality that a Benard cell is appropriately present on the surface of the surface layer of the charging member. As a result, the present invention has been completed.

The problem to be solved by the present invention is to provide a charging member for an electrophotographic device having excellent image quality and a method for manufacturing the charging member for an electrophotographic device.

To solve the above problems, the charging member for electrophotographic equipment according to the present invention comprises an elastic layer and a surface layer formed on the outer periphery of the elastic layer, and the surface layer is a modifier having a polyamide and a hydroxyl group. The modifier having a hydroxyl group is at least one of a fluorine-based modifier, a silicone-based modifier, and an acrylic-based modifier, and has a height of 0.1 to 1.0 μm on the surface of the surface layer. The gist is to have a Benard cell.

The modifier having a hydroxyl group is particularly preferably a fluorine-based modifier. The surface layer preferably contains roughness-forming particles, and the average particle diameter thereof is preferably in the range of 3.0 to 30 μm. The size of the Benard cell is preferably in the range of 250 to 1100 μm.

The method for producing a charging member for an electrophotographic device according to the present invention is the method for producing a charging member for an electrophotographic device according to the present invention, wherein the surface layer is a solute containing the modifier having the polyamide and the hydroxyl group. The coating liquid containing a mixed solvent of toluene and methanol as a solvent is applied to the outer periphery of the elastic layer, and then dried at a temperature of 100 to 150° C. for 30 to 60 minutes. Is the gist.

According to the charging member for an electrophotographic apparatus according to the present invention, the surface layer contains polyamide and a modifier having a hydroxyl group, and the modifier having a hydroxyl group is a fluorine-based modifier, a silicone-based modifier, and an acrylic-based modifier. Since it is at least one kind of agent and has a Benal cell having a height of 0.1 to 1.0 μm on the surface of the surface layer, the image quality is excellent.

FIG. 1A is an external schematic view of a charging roll for an electrophotographic apparatus according to an embodiment of the present invention, and FIG. FIG. 2 schematically shows the surface structure of the surface layer of the charging roll for electrophotographic equipment shown in FIG. 1, and is an enlarged view of the surface (a) and a cross-sectional view taken along line BB thereof (b). It is a modification which showed typically the surface structure of the surface layer of the electrification roll for electrophotographic equipment concerning the present invention, and is a surface enlarged view (a) and its CC sectional view (b). It is an example which showed typically the surface structure of the surface layer of the electrification roll for electrophotographic machines, and is a surface enlarged view (a) and its DD sectional view (b).

Hereinafter, the present invention will be described in detail. The shape of the charging member for electrophotographic apparatus according to the present invention is not particularly limited as long as it charges a member to be charged such as a photosensitive drum. For example, a roll shape, a plate shape, a block shape, or the like can be applied. A roll is particularly preferable. Hereinafter, a roll-shaped roll (charging roll) will be described as an example.

The charging roll for electrophotographic equipment according to the present invention (hereinafter, also simply referred to as charging roll) will be described in detail. FIG. 1 is an external schematic view (a) of a charging roll for an electrophotographic apparatus according to an embodiment of the present invention and a sectional view (b) taken along the line AA. FIG. 2 schematically shows the surface structure of the surface layer of the charging roll shown in FIG. 1, and is an enlarged view of the surface (a) and its cross-sectional view taken along the line BB (b).

The charging roll 10 includes a shaft body 12, an elastic body layer 14 formed on the outer circumference of the shaft body 12, and a surface layer 16 formed on the outer circumference of the elastic body layer 14. The elastic layer 14 is a layer serving as a base of the charging roll 10. The surface layer 16 is a layer that appears on the surface of the charging roll 10.

The surface layer 16 contains a modifier having a polyamide and a hydroxyl group, and has a Benard cell 18 having a height of 0.1 to 1.0 μm on the surface. When the surface layer 16 is formed, the Benard cell 18 is caused by a phenomenon in which a vortex flow is generated inside the coating film due to heating or the like, and as a result, a hexagonal cell structure appears mainly. The eddy current is generated in the vertical direction inside the coating film, and from the center to the outside on the coating film surface. The Benard cell 18 is an area surrounded by the cell wall 18a.

Polyamide is a binder polymer of the surface layer 16 and a base polymer. The surface layer 16 may contain a polymer other than polyamide as a binder polymer as long as it does not affect the present invention, but the binder polymer may be composed of only polyamide. Polyamide is a polymer having a relatively large surface free energy. Therefore, a coating film containing polyamide is likely to undergo the Benard cell phenomenon in the drying process. With other polymers, the Benard cell phenomenon does not easily occur. In the present invention, the Benard cells 18 are positively formed on the surface of the surface layer 16 by utilizing the properties of the coating film containing such a polyamide.

The type of polyamide is not particularly limited. Examples of the polyamide include nylon having an aliphatic skeleton and aramid having only an aromatic skeleton. Examples of nylon include n-nylon synthesized by polycondensation reaction of ω amino acid and n,m-nylon synthesized by copolycondensation reaction of diamine and dicarboxylic acid. Examples of n-nylon include nylon 6, nylon 11 and nylon 12. Examples of n,m-nylon include nylon 66. The polyamide may be modified or unmodified. Examples of the modifying group include an N-methoxymethyl group, a silicone group, a fluorine group and the like. Of these, N-methoxymethylated nylon is preferable from the viewpoint of high dielectric properties (chargeability).

The modifier having a hydroxyl group adjusts the surface tension of the coating film containing polyamide and adjusts the height of the Benard cell 18. It is presumed that this is because the modifier interacts with the polyamide through a hydroxyl group of the modifier through a hydrogen bond between molecules. With a modifier having no functional group or a modifier having another functional group and no hydroxyl group, the Benard cell phenomenon is suppressed even in a coating film containing polyamide, and the Benard cell 18 is not formed. A modifier having no functional group cannot intermolecularly interact with polyamide by hydrogen bond. It is speculated that other functional groups (for example, carboxylic acid groups) preferentially have intramolecular hydrogen bonds and have small intermolecular interaction with polyamide. In order to form the Benard cells 18 on the surface of the surface layer 16, a modifier having a hydroxyl group is necessary.

The modifier having a hydroxyl group may be solid or liquid at room temperature as long as it can be dissolved/dispersed in the coating film containing polyamide. The modifier having a hydroxyl group is more preferably a liquid at room temperature from the viewpoint of being more excellent in solubility and dispersibility. Examples of the modifier having a hydroxyl group include fluorine-based, silicone-based and acrylic-based modifiers. As the modifier having a hydroxyl group, only one of these may be used alone, or two or more thereof may be used in combination. Of these, fluorine type is more preferable. Due to the effect of suppressing the tackiness of the surface of the surface layer 16, the adhesion of the residual toner and the toner external additive is easily suppressed. Moreover, even if it adheres, it becomes easy to remove. Examples of the fluorinated modifier include fluorinated surfactants. Examples of the fluorine-based modifier include Megafac series manufactured by DIC. Examples of the silicone modifier include silicone oil and the like. Examples of the acrylic modifier include acrylic polymers and silicone acrylic polymers. The acrylic polymer is an acrylic homopolymer or acrylic copolymer composed of one or more of acrylic acid ester or methacrylic acid ester. The silicone acrylic polymer is a silicone-modified acrylic polymer.

In the surface layer 16, the content of the modifier having a hydroxyl group is 0.1 parts by mass or more with respect to 100 parts by mass of the polyamide, from the viewpoint of the excellent effect of forming the Benard cells 18 on the surface of the surface layer 16. preferable. The amount is more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass or more. The amount is preferably 3.0 parts by mass or less from the viewpoint of suppressing aggregation of the modifier and excellent dispersibility. The amount is more preferably 2.0 parts by mass or less, still more preferably 1.0 part by mass or less.

The Benard cells 18 are distributed on the surface of the surface layer 16 to suppress the concentration of contaminants locally. This is because the dirt substance is prevented from locally gathering around the roughness-forming particles or the like by sticking the dirt substance to the cell wall 18a of the Benard cell 18. The dirt substances are residual toner, external additives, and the like. The image quality is improved by not concentrating the dirt substance locally. The height of the Benard cell 18 is set to 0.1 μm or more. If the height is less than 0.1 μm, the dirt substance does not adhere to the cell wall 18a of the Benard cell 18, and the dirt substance cannot be suppressed from being locally collected. From this viewpoint, the height is more preferably 0.2 μm or more, further preferably 0.3 μm or more. On the other hand, the height of the Benard cell 18 is set to 1.0 μm or less. If the height is more than 1.0 μm, the surface roughness is greatly affected and the image quality is deteriorated. From this viewpoint, the height is more preferably 0.8 μm or less, further preferably 0.7 μm or less. The height of the Benard cell 18 is measured by observing the surface of the surface layer 16 with a laser microscope and measuring the height from the position of the maximum depth in the Benard cell 18 to the apex of the cell wall 18a. Expressed as an average.

The size of the Benard cell 18 is preferably 250 μm or more from the viewpoint of uniform charging property and the like. More preferably, it is 300 μm or more. Further, it is preferably 1100 μm or less from the viewpoint of uniform dispersibility and prevention of local stains. More preferably, it is 1000 μm or less. The size of the Benard cell 18 is obtained by observing the surface of the surface layer 16 with a laser microscope, measuring the longest distance from the apex of the cell wall 18a to its diagonal point, and expressing the average of 20 points of the arbitrary Benard cell 18.

The surface layer 16 may include roughness-forming particles for forming roughness on the surface layer 16. When the surface layer 16 contains the roughness-forming particles, the charging characteristics of the charging roll 10 can be further improved.

FIG. 3 shows a modification of the present invention in which the surface layer 16 includes the roughness-forming particles 20. FIG. 3A is an enlarged view of the surface of the surface layer 16, and FIG. 3B is a sectional view taken along the line C-C. Further, FIG. 4 shows an example of the charging roll in which the surface layer 16 includes the roughness-forming particles 20. FIG. 4A is an enlarged view of the surface of the surface layer 16, and FIG. 4B is a sectional view taken along the line DD of FIG.

As described above, in the charging roll 10 according to the present invention, the surface layer 16 contains a modifier having a polyamide and a hydroxyl group, and the surface thereof has a Benard cell 18 having a height of 0.1 to 1.0 μm. Since the height of the Benard cell 18 is 1.0 μm or less, unevenness of the roughness forming particles 20 in the boundary process of the cell (near the cell wall 18a) during the generation process of the Benard cell 18 is suppressed. Thereby, as shown in FIG. 3, the roughness-forming particles 20 are uniformly dispersed in the surface layer 16 regardless of the position of the cell wall 18a of the Benard cell 18. The roughness-forming particles 20 are evenly distributed in the surface layer 16 to ensure the uniformity of surface roughness and resistance. Thereby, the image quality is excellent. From this viewpoint, the height is more preferably 0.8 μm or less, further preferably 0.7 μm or less.

On the other hand, when the height of the Benard cell 18 is more than 1.0 μm, the roughness-forming particles are unevenly distributed in the cell boundary (near the cell wall 18a) during the generation process of the Benard cell 18, as shown in FIG. However, the surface roughness and the uniformity of resistance decrease. As a result, the uniform charging property is deteriorated and the image quality is deteriorated.

As the roughness forming particles 20, resin particles or the like are used. The material of the roughness forming particles 20 is not particularly limited, and acrylic particles, silicone particles, urethane particles and the like are used. The size of the roughness-forming particles 20 is not particularly limited, but it is preferable that the average particle size is 3.0 to 30 μm from the viewpoint of ensuring uniform chargeability. More preferably, the average particle size is 5.0 to 15 μm. The average particle diameter of the roughness-forming particles 20 is determined by observing the surface of the surface layer 16 with a laser microscope and using the diameter of the roughness-forming particles 20 that is visible during surface observation as the particle diameter. It is expressed as an average of 20 points. Further, the content of the particles 20 for forming roughness is not particularly limited, but from the viewpoint of easily ensuring uniform charging property, it is 10 to 100 parts by mass of the polyamide as the base polymer of the surface layer 16. It is preferably within the range of 50 parts by mass. It is more preferably in the range of 15 to 40 parts by mass.

The surface layer 16 may contain one or more kinds of various additives to be added to the surface layer 16, in addition to the modifier having a polyamide and a hydroxyl group, within a range that does not affect the present invention. Examples of such additives include conductive agents, fillers, stabilizers, ultraviolet absorbers, lubricants, release agents, dyes, pigments, flame retardants and the like.

Examples of the conductive agent include ionic conductive agents and electronic conductive agents. Examples of the ion conductive agent include quaternary ammonium salt, quaternary phosphonium salt, borate, and surfactant. As the electron conductive agent, carbon black, _{graphite, c-TiO 2, c-} ZnO, c-SnO 2 (c- means conductive.) And the like conductive oxides such as.

The surface layer 16 can be adjusted to have a predetermined volume resistivity by the material type, the blending of the conductive agent, and the like. The volume resistivity of the surface layer 16 may be appropriately set in the range of 10 ⁵ to 10 ¹¹ Ω·cm, 10 ⁸ to ¹⁰ 10 Ω·cm, etc. depending on the application. The thickness of the surface layer 16 is not particularly limited, and may be appropriately set within the range of 10 to 30 μm or the like depending on the application. The thickness of the surface layer 16 is the thickness in the portion where the roughness-forming particles do not exist.

The surface layer 16 can be formed by applying and drying the surface layer forming composition on the outer peripheral surface of the elastic layer 14. The surface layer forming composition contains a polyamide and a modifier having a hydroxyl group. In addition, the roughness-forming particles 20 are included as necessary. Further, if necessary, one kind or two or more kinds of various additives added to the surface layer are contained. Moreover, a solvent is included if necessary.

The height and size of the Benard cell 18 on the surface of the surface layer 16 can be adjusted by adjusting the component composition, solvent composition, viscosity, concentration, coating amount, film thickness, drying conditions (temperature, time, etc.) of the surface layer forming composition. , Can be adjusted. From the viewpoint of forming the Benard cells 18 having a specific height, and from the viewpoint of forming the Benard cells 18 having a predetermined size, the component composition contains a polyamide and a modifier having a hydroxyl group as a solute. Is preferred. The solvent composition preferably contains a mixed solvent of toluene and methanol as a solvent. The toluene/methanol mass ratio is preferably, for example, 3/1 to 1/3. The solid content concentration is preferably 5 to 30% by mass. The film thickness is preferably 2 to 25 μm. Moreover, as a drying condition, it is preferable to dry at a temperature of 100 to 150° C. for a time of 30 to 60 minutes.

The elastic layer 14 contains a crosslinked rubber. The elastic body layer 14 is formed of a conductive rubber composition containing uncrosslinked rubber. The crosslinked rubber is obtained by crosslinking uncrosslinked rubber. The uncrosslinked rubber may be a polar rubber or a non-polar rubber. From the viewpoint of excellent conductivity, the uncrosslinked rubber is more preferably a polar rubber.

The polar rubber is a rubber having a polar group, and examples of the polar group include a chloro group, a nitrile group, a carboxyl group and an epoxy group. Specific examples of the polar rubber include hydrin rubber, nitrile rubber (NBR), urethane rubber (U), acrylic rubber (copolymer of acrylic ester and 2-chloroethyl vinyl ether, ACM), chloroprene rubber (CR). , Epoxidized natural rubber (ENR) and the like. Among the polar rubbers, hydrin rubber and nitrile rubber (NBR) are more preferable from the viewpoint that the volume resistivity tends to be particularly low.

As the hydrin rubber, a homopolymer of epichlorohydrin (CO), an epichlorohydrin-ethylene oxide binary copolymer (ECO), an epichlorohydrin-allyl glycidyl ether binary copolymer (GCO), an epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary A copolymer (GECO) etc. can be mentioned.

Examples of the urethane rubber include polyether type urethane rubber having an ether bond in the molecule. The polyether type urethane rubber can be produced by reacting a polyether having hydroxyl groups at both ends with diisocyanate. The polyether is not particularly limited, and examples thereof include polyethylene glycol and polypropylene glycol. The diisocyanate is not particularly limited, but examples thereof include tolylene diisocyanate and diphenylmethane diisocyanate.

Examples of the non-polar rubber include isoprene rubber (IR), natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR) and the like.

Examples of the crosslinking agent include a sulfur crosslinking agent, a peroxide crosslinking agent, and a dechlorination crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.

Examples of sulfur crosslinking agents include conventionally known sulfur crosslinking agents such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, sulfur chloride, thiuram-based vulcanization accelerator, and polymer polysulfide. it can.

Examples of peroxide crosslinking agents include peroxyketals, dialkyl peroxides, peroxyesters, ketone peroxides, peroxydicarbonates, diacyl peroxides, hydroperoxides, and other conventionally known peroxide crosslinking agents. You can

Examples of the dechlorination crosslinking agent include dithiocarbonate compounds. More specifically, quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-isopropylquinoxaline-2,3-dithiocarbonate, 5,8-dimethylquinoxaline-2,3- Examples thereof include dithiocarbonate.

The amount of the cross-linking agent to be blended is preferably 0.1 to 2 parts by mass, and more preferably 0.3 to 1.8 parts by mass, based on 100 parts by mass of the uncrosslinked rubber, from the viewpoint of difficulty in bleeding. Parts, and more preferably 0.5 to 1.5 parts by mass.

When a dechlorination crosslinking agent is used as the crosslinking agent, a dechlorination crosslinking accelerator may be used together. Examples of the dechlorination crosslinking accelerator include 1,8-diazabicyclo(5,4,0)undecene-7 (hereinafter abbreviated as DBU) or its weak acid salt. Although the dechlorination crosslinking accelerator may be used in the form of DBU, it is preferably used in the form of its weak acid salt from the viewpoint of handling. As the weak acid salt of DBU, carbonate, stearate, 2-ethylhexylate, benzoate, salicylate, 3-hydroxy-2-naphthoate, phenol resin salt, 2-mercaptobenzothiazole salt, 2- Examples thereof include mercaptobenzimidazole salt.

The content of the dechlorination cross-linking accelerator is preferably in the range of 0.1 to 2 parts by mass based on 100 parts by mass of the uncrosslinked rubber from the viewpoint of difficulty in bleeding. It is more preferably within the range of 0.3 to 1.8 parts by mass, and even more preferably within the range of 0.5 to 1.5 parts by mass.

To give conductivity to the elastic layer 14, carbon black, graphite, c-TiO ₂ , c-ZnO, c-SnO ₂ (c- means conductivity), an ionic conductive agent (quaternary grade). Conventionally known conductive agents such as ammonium salts, borates, and surfactants) can be appropriately added. Further, various additives may be appropriately added as needed. As the additives, lubricants, vulcanization accelerators, antioxidants, light stabilizers, viscosity modifiers, processing aids, flame retardants, plasticizers, foaming agents, fillers, dispersants, defoamers, pigments, release agents. A mold agent and the like can be mentioned.

The elastic layer 14 can be adjusted to a predetermined volume resistivity by the type of crosslinked rubber, the amount of ionic conductive agent, the amount of electronic conductive agent, and the like. The volume resistivity of the elastic body layer 14 may be appropriately set in a range of 10 ² to 10 ¹⁰ Ω·cm, 10 ³ to 10 ⁹ Ω·cm, 10 ⁴ to 10 ⁸ Ω·cm, etc. depending on the application. ..

The thickness of the elastic layer 14 is not particularly limited, and may be appropriately set within a range of 0.1 to 10 mm depending on the application. The elastic layer 14 may be foam or non-foam.

The elastic body layer 14 can be manufactured as follows, for example. First, the shaft body 12 is coaxially installed in the hollow portion of the roll molding die, and the uncrosslinked conductive rubber composition is injected, heated and cured (crosslinked), and then demolded, or The elastic body layer 14 is formed on the outer periphery of the shaft body 12 by extruding an uncrosslinked conductive rubber composition on the surface of the shaft body 12.

The shaft body 12 is not particularly limited as long as it has conductivity. Specific examples thereof include solid bodies made of metal such as iron, stainless steel, and aluminum, cores made of hollow bodies, and the like. An adhesive, a primer or the like may be applied to the surface of the shaft body 12 if necessary. That is, the elastic body layer 14 may be adhered to the shaft body 12 via the adhesive layer (primer layer). The adhesive, the primer and the like may be made conductive if necessary.

According to the charging roll 10 having the above configuration, the surface layer 16 contains the modifier having a polyamide and a hydroxyl group, and the surface has the Benard cells 18 having a height of 0.1 to 1.0 μm. It is possible to prevent the dirt substance from adhering to and to locally collect the dirt substance. Moreover, the influence on the surface roughness can be suppressed. Thereby, the image quality is excellent. When the surface layer 16 contains the roughness-forming particles 20, since the height of the Benard cells 18 is 1.0 μm or less, the roughness-forming particles 20 are generated at the boundary portion of the cells (cells) during the generation process of the Benard cells 18. Uneven distribution in the vicinity of the wall 18a) is suppressed. As a result, the roughness-forming particles 20 are uniformly dispersed in the surface layer 16 regardless of the position of the cell wall 18a of the Benard cell 18. The roughness-forming particles 20 are evenly distributed in the surface layer 16 to ensure the uniformity of surface roughness and resistance. Thereby, the image quality is excellent.

The configuration of the charging roll according to the present invention is not limited to the configuration shown in FIG. For example, the charging roll 10 shown in FIG. 1 may have a configuration in which another elastic body layer is provided between the shaft body 12 and the elastic body layer 14. In this case, the other elastic layer is a layer serving as a base of the charging roll, and the elastic layer 14 functions as a resistance adjusting layer for adjusting the resistance of the charging roll. The other elastic layer can be made of, for example, any of the materials listed as the material of which the elastic layer 14 is made. Further, for example, the charging roll 10 shown in FIG. 1 may have a configuration in which another elastic layer is provided between the elastic layer 14 and the surface layer 16. In this case, the elastic layer 14 is a layer that serves as a base of the charging roll, and the other elastic layers function as a resistance adjusting layer that adjusts the resistance of the charging roll.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

(Examples 1 to 11)
<Preparation of conductive rubber composition>
5 parts by mass of a vulcanization aid (zinc oxide, Mitsui Kinzoku "Zinc oxide type 2") to 100 parts by mass of hydrin rubber (ECO, Daiso "Epichromer CG102"), carbon (Ketjen Black International "Ketjen" 10 parts by mass of black EC300J", 0.5 parts by mass of a vulcanization accelerator (2-mercaptobenzothiazole, "NOXCELLER MP" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., " 2 parts by mass of Sulfax PTC") and 50 parts by mass of a filler (calcium carbonate, "Shiragika CC" manufactured by Shiraishi Kogyo Co., Ltd.) were added, and these were stirred and mixed by a stirrer to prepare a conductive rubber composition.

<Preparation of elastic layer>
A core metal (shaft, diameter 6 mm) is set in a molding die (pipe shape), the above-mentioned conductive rubber composition is injected, and after heating at 180° C. for 30 minutes, the core metal is cooled and demolded. An elastic layer having a thickness of 1.9 mm was formed on the outer periphery of the.

<Preparation of surface layer forming composition>
The binder polymer, the modifier, and the particles for forming roughness are blended so as to have the formulation (parts by mass) described in Table 1, and the mixed solvent of toluene and methanol (mass ratio is 20% by mass of the solid content concentration). The concentration was adjusted by 1:2). The solid content concentration is the total concentration of components other than the solvent.

<Preparation of surface layer>
The surface layer-forming composition was roll-coated on the surface of the elastic layer and heated at 130° C. for 50 minutes to form a surface layer having a thickness of 10 μm on the outer periphery of the elastic layer. Thereby, the charging rolls according to Examples 1 to 11 were manufactured. The thickness of the surface layer is the thickness in the portion where the roughness-forming particles do not exist.

(Example 12)
In preparation of the surface layer forming composition, a charging roll according to Example 12 was produced in the same manner as in Examples 1 to 11 except that the roughness forming particles were not blended as described in Table 1.

(Examples 13 to 14)
In the preparation of the surface layer forming composition, charging rolls according to Examples 13 to 14 were produced in the same manner as in Examples 1 to 11 except that the solid content concentration was changed as shown in Table 1.

(Example 15)
A charging roll according to Example 15 was produced in the same manner as in Examples 1 to 11 except that the electronic conductive agent was blended as shown in Table 1 in the preparation of the surface layer forming composition.

(Comparative Example 1)
Comparative Example 1 was carried out in the same manner as in Examples 1 to 11 except that a modifier having no hydroxyl group and having a carboxylic acid group was used in place of the modifier having a hydroxyl group in the preparation of the surface layer forming composition. The charging roll according to the above was produced.

(Comparative example 2)
In the preparation of the surface layer forming composition, a charging roll according to Comparative Example 2 was produced in the same manner as in Examples 1 to 11 except that an unmodified modifier was used instead of the modifier having a hydroxyl group.

(Comparative example 3)
A charging roll according to Comparative Example 3 was produced in the same manner as in Examples 1 to 11 except that the modifier was not mixed in the preparation of the surface layer forming composition.

(Comparative Example 4)
A charging roll according to Comparative Example 4 was produced in the same manner as in Comparative Example 3 except that the binder polymer was changed in the preparation of the surface layer forming composition.

(Material of the surface layer forming composition)
-Binder 1 (binder polymer): N-methoxymethylated nylon (manufactured by Nagase Chemtex, "EF30T")
Binder 2 (binder polymer): Fluorine resin ("Neotron PFA" manufactured by Daikin Industries, Ltd.)
-Modifier 1: Fluorine-based modifier having a hydroxyl group ("Megafuck F-477" manufactured by DIC)
-Modifier 2: Acrylic modifier having hydroxyl group ("SD-10" manufactured by Toagosei)
-Modifier 3: a silicone-based modifier having a hydroxyl group ("XF42-B0970" manufactured by Momentive Performance Materials)
-Modifier 4: a silicone-based modifier having a carboxylic acid group ("X-22-3701E" manufactured by Shin-Etsu Silicone)
-Modifying agent 5: unmodified silicone type modifying agent ("KF-96L-1cs" manufactured by Shin-Etsu Silicone, dimethyl silicone oil)
・Electron conductive agent: Carbon black, "Diablack #3030" manufactured by Mitsubishi Chemical Corporation

The surface of the surface layer of each of the produced charging rolls was observed to confirm the occurrence of Benard cells and the dispersed state of the particles for forming roughness. In addition, the height and size of the Benard cells and the particle size of the roughness-forming particles were measured. In addition, image evaluation was performed. The evaluation results and the compounding composition (parts by mass) of the surface layer forming composition are shown in the following table.

(Surface observation)
The surface of the surface layer of the charging roll was observed with a commercially available laser microscope (color 3D laser microscope “VK-8710” manufactured by Keyence). The measurement magnification was 400 times, the measurement pitch was 0.1 μm, and the laser light amount was 1000.

(Benard cell height)
At the time of observing the surface, the height from the position of the maximum depth in the Benard cell to the apex of the cell wall was measured and expressed as an average of 20 arbitrary Benard cells.

(Size of Benard cell)
At the time of observing the surface, the longest distance from the apex of the cell wall to its diagonal point was measured and expressed as an average of 20 arbitrary Benard cells.

(Size of particles for forming roughness)
The diameter of the roughness-forming particles seen when the surface was observed was defined as the particle diameter, and the average of 20 points of arbitrary roughness-forming particles was used.

(Image evaluation)
Each charging roll was incorporated into a commercially available full-color MFP, and an image was printed with a halftone print pattern in an environment of 25° C.×50% RH. The initial evaluation and the evaluation after 10,000 sheets of durability were evaluated. If the image had no horizontal stripes, it was evaluated as “good”, and if the image had horizontal stripes even at one place, it was evaluated as “poor”. In addition, each charging roll was incorporated into a commercially available full-color MFP, left for 30 days in an environment of 25° C. and 50% RH, and then image evaluation was performed. As a result of evaluating the image of the portion corresponding to the contact portion with the photosensitive drum, one having no horizontal stripe in the image at the photoconductor pitch was evaluated as good “◯”, and one having horizontal stripe in the image was evaluated as poor “x”. ..

From Examples and Comparative Examples, when the coating film containing polyamide did not contain a modifier (Comparative Example 3), the height of Benard cells was large and the particles for forming roughness were unevenly distributed in the vicinity of the cell walls (Fig. 4). For this reason, the surface roughness and the uniformity of the resistance were lowered, and the streak image was generated from the beginning due to the reduction of the uniform charging property. As a result, no test was performed after the contact was left. Further, when the coating film containing polyamide only contains the non-modified modifier (Comparative Example 2), Benard cells were not generated, and the stain substances such as the residual toner and the external additive caused the bottom portion of the particles for forming roughness. Locally, the streaked image was generated after the endurance. Further, when the coating film containing polyamide contains only the modifier having a functional group other than hydroxyl group such as carboxylic acid group (Comparative Example 1), Benard cells are not generated, and the residual toner and the stain substances such as external additives are not generated. The roughness-forming particles were locally aggregated at the hem and the like, and a streak image was generated after running. On the other hand, by including a modifier having a hydroxyl group in the coating film containing polyamide (Example), a Benal cell having a predetermined height is formed on the surface of the surface layer, and the Benal cell stains residual toner and external additives. Material no longer concentrates locally. Further, the particles for forming roughness were not unevenly distributed in the vicinity of the cell wall, but were uniformly dispersed on the surface of the surface layer (see FIG. 3). As a result, the generation of streak images was suppressed at the initial stage and after endurance. Further, even after being left in the contact state, generation of streak images is suppressed. It is speculated that this is because the hydroxyl group of the modifier appearing on the surface interacts with the polyamide of the binder polymer through a hydrogen bond to cause intermolecular interaction, so that transfer to the photosensitive drum is suppressed. Such effects cannot be obtained with a modifier having another functional group or a non-modified modifier. For example, in Comparative Examples 1 and 2, it is found that horizontal streaks are generated even after being left in the contact state, and the modifier is transferred to the photosensitive drum. Further, from Comparative Example 4, in the binder polymer other than polyamide, the generation of Benard cells is suppressed without adding a modifier. However, since the Benard cells are not generated, the generation of streak images after endurance cannot be suppressed.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. ..

10 Charging Roll 12 Shaft 14 Elastic Layer 16 Surface Layer 18 Benard Cell 20 Roughness Forming Particles

Claims (5)

An elastic layer, and a surface layer formed on the outer periphery of the elastic layer,
The surface layer contains a polyamide and a modifier having a hydroxyl group, and the modifier having a hydroxyl group is at least one of a fluorine-based modifier, a silicone-based modifier, and an acrylic-based modifier, and the surface of the surface layer. A charging member for electrophotographic equipment, which has a Benard cell having a height of 0.1 to 1.0 μm. The charging member for electrophotographic equipment according to claim 1, wherein the modifier having a hydroxyl group is a fluorine-based modifier. The charging member for an electrophotographic apparatus according to claim 1, wherein the surface layer contains particles for forming a roughness, and the average particle diameter thereof is within a range of 3.0 to 30 μm. The charging member for electrophotographic equipment according to claim 1, wherein the size of the Benard cell is within a range of 250 to 1100 μm. A method of manufacturing a charging member for electrophotographic equipment according to any one of claims 1 to 4,
The surface layer is coated with a coating liquid containing the polyamide and the modifier having a hydroxyl group as a solute and a mixed solvent of toluene and methanol as a solvent on the outer periphery of the elastic layer, and then at a temperature of 100 to 150° C. A method for producing a charging member for an electrophotographic apparatus, which is formed by drying for 30 to 60 minutes.

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